Gun having a launching tube provided with a partial vacuum sink tank



Jan- 26, 1965 J. J. MURRAY 3,167,061

GUN HAVING A LAUNCHING TUBE PROVIDED WITH A PARTIAL VACUUM SINK TANK Filed April 9, 1963 Remb/ual air INVENTOR. James l murra United States Patent O 3,1e7,061 Y GUN HAVING A LAUNCHENG TUE@ YRVGE* WTH A FARTHAL VACUM SENK TANK .lames d. Murray, @iig Hudson St., Denham, NuC. Filed Apr. 1963, Ser. No. 271,@29 S rCiairns. (Ci. 12d-11) (Granted under Title 3S, ELS. Code @952), see. 25d) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to a partial vacuum sink tank and in particular to a sink tank for the launching tube of a gun of the type in which the projectile is propelled through a launching tube by Iatmospheric pressure.

The principle of operation of the above mentioned type gun is as follows: a projectile is placed in the gun tube and the tube is sealed at the muzzle end by a disc of synthetic resinous material. The projectiles base seals the breech end and is retained at the breech end by a suitable trigger or the like. The tube is then evacuated to a small fraction of its atmospheric pressure. The retaining trigger releases the projectile which will then be propelled through the tube by the outside air pressure. The projectile exits from the tube at the muzzle end, shattering the disc and follows a ballistic trajectory governed by several parameters such as atmospheric pressure, the tubes residual partial pressure, slidingr friction in the tube and shattering force on the disc. A gun operating on this principle is disclosed in U.S. Patent No. 422,347 issued February 25, 1890.

The aforesaid gun was not eflicient due to the fact that the projectile would act as a piston and compress the residual air in the tube in the vicinity of the muzzle end of the launching tube. ln compressing this trapped air column, the projectile would, naturally, expend energy doing work which is translated into power expenditure in terms of rate of movement. Obviously this energy waste would detract from the muzzle velocity of the projectile.

The present invention proposes to significantly reduce the rapid build-up of back pressure against the projectiles nose by a sink tank, which has been evacuated to the same pressure as the launching tube and is connected directly on the launching tube near the muzzle end thereof so as to provide a large volume capacity for residual air compressed by the projectile in its piston like action in moving through the evacuated launching tube.

It is therefore a primary object of this invention to reduce the rapid build-up of back pressure against the projectiles nose in the launching tube of a gun in which the projectile is driven therethrough by atmospheric pressure.

Another object of the invention is to provide a sink tank near the muzzle of a gun in which the projectile is driven by atmospheric pressure.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawing in which:

FIG. 1 is a schematic cross section of a gun operated by atmospheric pressure and is illustrated by Way of example only to illustrate the principle of its operation;

FIG. 2 is a partial section of the muzzle end of a gun of the type shown in FIG. 1 and showing the sink tank of the invention applied thereto; and

FlG. 3 is a similar view showing a modified form of sink tank.

Referring now to FIG. l of the drawing, reference character 1 indicates generally ra gun operated by atmospheric pressure and vacuum.

Gun 1 includes a launching tube 2 which is open at both ends and is provided with a trigger device indicated ice generally by 3 of any suitable design, and as shown by way of example, and consists of a handle 4 which is pivoted in ears 5. A rod 6 is pivotally attached to handle 4 at '7.

Tube 1 is further provided with an evacuating port 8 for attachment to a hose or the like for connection to an evacuating pump, not shown. An O-ring 17 completes the assembly.

The operation of the gun of FIG. 1 is simple. A plastic disc 9 is placed over the muzzle of the gun to seal it at that end. A smear of silicon grease or the like may be used to adhese the disc to the muzzle. Then a projectile 1u is inserted at the breech end and pushed beyond the G-ring 17, or it may be inserted at the muzzle end before applying disc 9 The projectile 10 may be provided with a lug 11 at its rearward end and this lug may have a hole (not shown) in it so that rod 6 may be inserted therethrough by manipulation of handle 4 to retain the projectile at the breech end of tube 1 until it is ready to be released. The rearward end of projectile 1li is shown to be planar and seals against O-ring 17 to complete the hermetical sealing of the tube 1. A hose (not shown) is connected at one end to port 3 and at its other end to an air evacuating pump, not shown.

The tube is then evacuated of air to a small fraction .of the atmospheric pressure. The gun is now ready to be red. The handle 4 is lifted (as shown in dotted lines in FIG. l) thus pulling rod 6 out of lug 11 which releases the projectile 1t). Now the ouside air pressure pushes projectile 163 4down the tube 1 where it shatters disc 9 and thereupon follows a ballistic trajectory.

The sink tank of the invention is shown in FIG. 2, and requires but little modification of the gun shown in FIG. 1.

The sink is indicated generally by reference character 12. The tank is an enclosure 13 and is connected to tube 1 by a tube 14. Port 8 is removed from its position shown in FIG. l and placed on tank 12 as at 15.. Sink tank 12 has a comparable volume to that of tube 1 and is evacuated to the same internal pressure as tube 1.

When the projectile 1t) has been released by trigger 3 (see FIG. l) the projectile 10 accelerates: up the tube 1, driven by the pressure difference PA-P1, Pi being the degree to which the internal pressure in tube 1 has been reduced by the air evacuation therein. The projectile 10 pushes the residual air at pressure P1 ahead of its changing position in tube 1, driving that air mass into sink tank 12 (which initially had been evacuated to the same internal pressure) thereby preventing the build-up of a significant back pressure upon projectile 10. With the sink tank 1u of comparable volume to that of the tiring tube 1, rand reduced to the same internal pressure by evacuation, the final sink tank pressure is increased only by an approximate factor of two. As an example, having the sink tank and launching tube at the same volume and the initial pressure of 1.0 psi., then the final pressure at the sink tank when the projectile is at the inlet tube 14 to sink tank 12, then that pressure will be 2 p.s.i.

It is evident that without the sink tank,` under the same conditions that where would be a rapid increase in internal pressure ahead of the moving projectile since the compressive action of the projectile would reduce the internal volume to near zero capacity. This action would adversely affect the projectiles maximum velocity in the launching tube due to energy expended in such a com pression of the gas.

FlG. 3 illustrates Ia modified form of sink tank.` The tank is indicated by 18 and is coaxially arranged around tiring tube 1. Holes 16 are provided in tube 1 to permit escape of the back pressure ahead of the projectile into the tank. (Port 8 need not be relocated in this form.)

What is claimed is:

1. A gun including in combination, a launching tube for launching a projectile therethrough; releasable retaining means mounted at the breech end of said tube for releasably retaining the Iprojectile at the breech end of said'tube'; .la first sealing means for sealing the muzzle end of said tube; a second means for sealing the breech end of said tube and a sink tank mounted adjacent the muzzle end of said tube, there `being an evacuating port in communication with said tube and disposed in advance of the projectile when said projectile is in its retained position in said tube whereby when said tube and said tank are partially evacuated of air therein, and said releasable retaining means is operated to' release `said projectile, the projectile will be propelled forward in said tube by the atmospheric pressure outside said tube and shatter said iirst sealing means and follow a ballistic trajectory, the residual air in said tube, inadvance of the projectile, being forced into said tank by said projectile.

2. The device of claim 1 wherein the first sealing means for sealing the muzzle end of said tube comprises a disc adhering to the face of said muzzle of said tube.

3. The device of claim 1 wherein the second sealing d. means for sealing the breechend of said tube comprises an O-ring secured within said tube and disposed adjacent the breech end thereof, said O-ring abutting the rearward face of a projectile, when in its launching position in said tube.

4. The device of claim 1 wherein said sink tank comprises an enclosure having a volume comparable to the volume of said tube, a tube connecting said tank to the forward portion of said tube and disposed adjacent the muzzle end thereof, said tank having a evacuating port therein. i

5. The device of claim 1 wherein said sink tank comprises an annular enclosure secured around the f orward portion of said tube and disposed adjacent the muzzle end thereof, there being a series of ports in the forward portion of said tube and in communication with said sink tank.

DELBERT B. LOWE, Primary Examiner. 

1. A GUN INCLUDING IN COMBINATION, A LAUNCHING TUBE FOR LAUNCHING A PROJECTILE THERETHROUGH; RELEASABLE RETAINING MEANS MOUNTED AT THE BREECH END OF SAID TUBE FOR RELEASABLY RETAINING THE PROJECTILE AT THE BREECH END OF SAID TUBE; A FIRST SEALING MEANS FOR SEALING THE MUZZLE END OF SAID TUBE; A SECOND MEANS FOR SEALING THE BREECH END OF SAID TUBE AND A SINK TANK MOUNTED ADJACENT THE MUZZLE END OF SAID TUBE, THERE BEING AN EVACUATING PORT IN COMMUNICATION WITH SAID TUBE AND DISPOSED IN ADVANCE OF THE PROJECTILE WHEN SAID PROJECTILE IS IN ITS RETAINED POSITION IN SAID TUBE WHEREBY WHEN SAID TUBE AND SAID TANK ARE PARTIALLY EVACUATED OF AIR THEREIN, AND SAID RELEASABLE RETAINING MEANS IS OPERATED TO RELEASE SAID PROJECTILE, THE PROJECTILE WILL BE PROPELLED FORWARD IN SAID TUBE BY THE ATMOSPHERIC PRESSURE OUTSIDE SAID TUBE AND SHATTER SAID FIRST SEALING MEANS AND FOLLOW A BALLISTIC TRAJECTORY, THE RESIDUAL AIR IN SAID TUBE, IN ADVANCE OF THE PROJECTILE, BEING FORCED INTO SAID TANK BY SAID PROJECTILE. 